1. Field of the Invention
This invention relates to a method for structuring the surface of a substrate, whereby the substrate is prepared and then the structure is produced on a surface area of the substrate by applying at least one solution to the surface area, which solution contains at least one solid substance dissolved in a solvent, whereby the solvent is removed from the surface of the substrate so that the solid substance remains behind.
2. Description of the Prior Art
A similar method of the prior art for the manufacture of a biochip is described in T. Vo-Dinh et al., “DNA Biochip Using a Phototransistor Integrated Circuit,” Analytical Chemistry, Volume 71, No. 2,p. 358 ff. (Jan. 15, 1999). In that case, first a microarray is created by applying, on a nitrocellulose membrane that functions as the substrate, a structure that has a matrix with a plurality of fields in which different biological receptors are located. For the manufacture of the micro array, the receptors are deposited on the substrate in liquid form by means of a capillary needle that is connected with a pico pump. The capillary needle has a capillary diameter of approximately 100 μm, so that the structure size of the fields that can be applied to the substrate by means of the capillary model lies in the range of approximately 100 μm. The micro array is used for the qualitative and/or quantitative detection of the presence of certain ligands in a sample to be analyzed. The receptors of the individual areas differ from one another in their specificity for a determined ligand to be detected. It is thereby possible to use the micro array to test the sample for the presence of a plurality of different ligands simultaneously. For the detection of a ligand that is contained in the sample, the sample is placed in contact with the receptors immobilized on the micro array. The receptor, which is specific for the ligand to be detected, thereby bonds to the ligands. The receptor-ligand complex formed can be detected by means of fluorescence. For the detection, the individual areas of the matrix that contain the receptors are irradiated with optical radiation which excites the receptor-ligand complexes to emit luminescent radiation. For the detection of the luminescent radiation, the micro array is positioned on the surface of a CCD sensor array so that the individual fields of the micro array each coincide with a photo cell of the CCD sensor array. One disadvantage of this arrangement, however, is that the fields of the matrix still have relatively large dimensions which—as noted above—are in the range of approximately 100 μm. However, the structure sizes of a typical CCD sensor array are only approximately 1 μm. Therefore if a micro array with 1000×1000 fields were positioned on a CCD sensor array, a chip surface of 100×100 mm would be required simply for the phototransistor array of the CCD sensor, which would make such a semiconductor chip very expensive and unprofitable.
DE 199 59 346 A1 describes a method in which the surface of a substrate is provided with a masking layer that is impermeable for a layer to be applied, and the substance is then introduced into areas of the substrate that are not covered by the masking layer. Then a heat treatment is performed, in which the substance is diffused into an area of the substrate covered by the masking layer. A concentration gradient of the substance is then formed, starting from the edge of the masking layer, with increasing distance inward from the edge in the area covered by the masking layer. Then the masking layer is removed to expose the substrate area underneath. Then a layer of the substrate close to the surface located in the exposed substrate area is converted by means of a chemical conversion reaction into a coating with a layer thickness profile that corresponds to the concentration gradient in the substance. Then the coating is placed in contact with an etching agent until in a partial area of the coating, the surface of which is smaller than the substrate area covered by the original masking layer and in which the thickness of the coating is reduced compared to the other areas, the substrate area covered by the partial area is exposed. After the coating in certain areas has been removed in this manner, in the exposed area of the surface a metal layer is electrically deposited, the dimensions of which are smaller than the dimensions of the original masking layer. In practice, this method has been found to be successful, in particular for the manufacture of small metal electrodes. One disadvantage of the method, however, is that it is relatively complex and time-consuming and that it is limited to certain substrate materials. In particular, the method is unsuitable in practice for the application of a structure that has biocomponents on the substrate.
Périchon, Lacour, Stéphanie et al., “Stretchable gold conductors on elastomeric substrates,” Applied Physics Letters, Volume 82, No. 15,pages 2404-2406, also describes a method for the manufacture of a stretchable electrical conductor which has, on an elastic substrate, thin gold strips to which a compression stress is applied. For the application of the compression stress, the substrate is first pre-stretched. Then the gold strip conductors are deposited onto the substrate through a shadow mask. Then the expansion of the substrate is reversed and the electrical conductivity of the gold contact strips is tested. On the basis of this test, the authors come to the conclusion that it is possible to manufacture expandable electrical conductors for use in three-dimensional electronic circuits.
The object of the invention is to create a method of the type described above that makes it possible, in a simple manner, to produce a structure with reduced structure size on the substrate.